Scientists fear an expansion in fish-farming on Tasmania's west coast could pose a threat to a rare bottom-dwelling skate dubbed the 'thylacine of the sea'.

Professor Graham Edgar discovered the Maugean skate, also known as the Port Davey skate, in 1988, and says it is one of the rarest marine animals in the world.

The species only lives in two places - Macquarie Harbour and Bathurst Harbour.

"There's no other shark or ray that lives in such a confined area," Professor Edgar said.

Dr Neville Barrett from the Institute of Marine and Antarctic Studies recently found a strong population of the species in Macquarie Harbour but says the area is the site of fish farm expansion and pressure from recreational fishing.

"This is ultimately the canary in the coal mine. The skate relies on a clean ocean environment, but then so do salmon farmers, so hopefully the can coexist," Dr Barrett said.

"We are aware that the harbour isn't - as some people perceive it - a highly impacted estuary from the mining activities.

"It's actually quite pristine, the vast majority of it, and it's an extremely important habitat of course for this species that lives nowhere else on earth."

Tasmanian salmon growers spokesman Adam Main says the industry is already working to protect the skates.

"They tend to like shallower water, so we've already made those concessions and moved farms out to deeper water," Mr Main said.